<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no">
    <meta name="author" content="helang.love@qq.com">
    <title>移动端 1px(线条/边框) 解决方案</title>
    <style type="text/css">
        body{
            margin: 0;
            padding: 0;
            font-size: 14px;
            color: #333;
            font-family: 'Microsoft YaHei', 'Times New Roman', Times, serif;
        }
 
        /* 线条 */
        .list{
            margin: 0 20px;
            list-style: none;
            line-height: 42px;
            padding: 0;
        }
        .list>li{
            padding: 0;
            position: relative;
        }
        .list>li:after{  
            content: "";
            display: block;
            height: 1px;
            background-color: #999;
            /* border-top: #999 solid 1px; */
            width: 100%;
            position: absolute;
            top: 0;
            right: 0;
            transform: scaleY(0.5); /* 将 1px 的线条缩小为原来的 50% */
        }
 
        /* 边框 */
        .button{
            line-height: 42px;
            text-align: center;
            margin: 20px;
            background-color: #f8f8f8;
            position: relative;
            border-radius: 4px;
        }
        .button:after{
            content: "";
            position: absolute;
            top: -50%;
            right: -50%;
            bottom: -50%;
            left: -50%;
            border: 1px solid #999;
            transform: scale(0.5);
            transform-origin: 50% 50% 0;
            box-sizing: border-box;
            border-radius: 8px; /* 尺寸缩小 50%，即圆角半径设置为按钮的2倍 */
        }
    </style>
</head>
<body>
<ul class="list">
    <li>线条 1px</li>
</ul>

<div style="border:1px solid #ccc">
    1px
</div>
<div class="button">边框 1px</div>
</body>
</html>